Sling



FIG. 1 is a front perspective view illustrating my design for a sling;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a top view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a bottom view thereof; and,

FIG. 7 is a rear elevational view thereof. 

The ornamental design for a sling, as shown and described. 